LOCAL ANESTHESIA
Local anesthesia is a condition of insensibility brought about in
a part of the body by the use of agents called local anesthetics.
The person in whom the local anesthesia is produced does not lose
consciousness as in general anesthesia, the part alone being made
insensible.
There are many agents which, when applied to a part, by one means
or another, cause that part to become insensible to pain, but for
the podiatrist the following agents are best calculated to serve his
purposes: cocaine, novocaine, alypin and urea hydrochloride, ethyl
chloride, ethyl bromide, carbon dioxide snow, apothesine and ice. (See
footnote page 148.)
_Cocaine_ is an alkaloid extracted from coca leaves. These latter are
not to be confused with cocoa, the seed of the chocolate tree. When
cocaine is treated with hydrochloric acid, hydrochloride of cocaine is
produced which occurs in a white crystalline powder, soluble in water
and alcohol. When injected into the skin, or applied to an open wound,
it acts as a paralyzant to the vasodilators and as a stimulant to the
vasoconstrictors. When applying this drug, a tourniquet should be used
wherever possible, so as to prevent absorption. This precaution is
essential, as cocaine[2] is very toxic, and even small quantities may
produce bad effects in some persons. There are cases on record in which
¹⁄₁₀₀ of a grain of this drug has produced all the symptoms of toxemia,
whereas there are persons who can stand doses up to one grain. It is
therefore essential to use judgment and care in administering a drug
which on account of the idiosyncrasies of some people, is likely, even
in minute doses, to produce serious, if not fatal symptoms.
In podiatry, a ¹⁄₂% solution is strong enough for general use, provided
that time enough is allowed for the drug to be diffused. For an
ordinary ingrown toe nail, two cubic centimeters of the above solution
is usually sufficient to produce anesthesia of the part.
_Novocaine_ is a synthetic preparation and occurs in colorless needles.
It can be heated to 120 degrees Centigrade, without undergoing
decomposition, which is not the case with cocaine hydrochloride.
Although not quite as efficient as an anesthetic, novocaine is only ¹⁄₇
as toxic as cocaine and therefore can be used with greater safety and
podiatrists generally have abandoned cocaine for novocaine. It has a
slightly irritating action while being injected, but on the whole it is
preferable to cocaine for podiatry practice. Physiologically, it has
the same action as cocaine, and is indicated wherever the latter drug
is used. It is usually injected in one per cent. solutions.
_Alypin_ occurs as a crystalline powder. It is a most efficient
anesthetic and because of its non-toxic action, it is to be preferred
in cases in which there is a fear of toxemia. Maximilian Stern, M.D.,
Professor of Surgery at the First Institute of Podiatry, has used this
drug extensively for producing local anesthesia, and his results have
been very satisfactory. For use in podiatry, a ¹⁄₄ to ¹⁄₈ per cent.
solution is often sufficient. It may be used freely in ¹⁄₄ per cent.
strength without danger of toxemia. When injected, it produces no
anemia, and consequently there is no danger of subsequent hemorrhage,
such as might accompany the use of either cocaine or novocaine.
_Quinine and urea hydrochloride_ is one of the quinine salts,
consisting of one molecule of quinine hydrochloride and one molecule
of urea. It has no toxic action when injected into the tissues, but it
retards healing, and scar tissue forms over operated areas where it has
been used. Many operators prefer this drug on account of its non-toxic
action when used in large quantities, despite the likelihood of a scar
and slow union. In parts of the body where contraction of the tissues
is a desirable after-effect (such as would be the case in hemorrhoids),
quinine and urea hydrochloride is to be preferred over other local
anesthetics. David H. Levy, M.D., a well known surgeon of New York
City, prefers it to all other local anesthetics.
_Ethyl chloride_ and _ethyl bromide_ are clear volatile liquids, and
upon their rapid evaporation depend their anesthetic qualities. When
a substance evaporates rapidly, it extracts the heat from surrounding
bodies in doing so, and, consequently, when such a substance is applied
to the skin, it soon extracts the heat from the part and with the
local anemia thus produced, sensation is lost. Ethyl chloride and
ethyl bromide are manufactured in tubes so arranged as to eject a fine
stream of the liquid. When this stream comes in contact with the skin,
evaporation is rapid and gradually the part becomes numb; continued,
it becomes frozen. This method is not as efficient as the hypodermic
injection because the anesthesia is not so lasting, moreover, the
reaction is severe and painful. Otto Sjogren and Fred Schmitt,
practitioners of known repute, have entirely discarded both of these
drugs from their list of local anesthetics, for reasons above mentioned.
_Carbon dioxide snow_ is prepared by allowing liquified carbon dioxide
gas to slowly escape from its container into a glove finger, where it
solidifies into a mass, assuming the shape and form of the receptacle;
it is called the _carbon dioxide pencil_. When this mass or pencil is
applied to a part, it extracts the heat and anesthetizes by freezing.
The dangers attending the use of the carbon dioxide pencil are the same
as with ethyl chloride or ethyl bromide and, due to its extremely low
temperature, there is danger of causing death of the tissues and of
producing conditions giving rise to subsequent ulcerations that are
slow to heal. As an anesthetic, it is not advised for podiatry.
=Technic of Producing Local Anesthesia.= There are three methods of
producing local anesthesia: (1) the hypodermatic method: (2) the
pressure method: (3) freezing.
The freezing method is of no great value to the podiatrist, and having
been already briefly described, further comment is deemed unnecessary.
The pressure method of producing local anesthesia is new, and although
extensively employed in the practice of dentistry, podiatry offers but
little opportunity for its free use. It is necessary to have an exposed
nerve, such as is found in the cavities of painful teeth, or an open
wound into which the drug can be absorbed, before this method can be
used. In cases of ingrown toe nail, in which the groove is lacerated,
either by the patient or by the nail itself, pressure anesthesia is
often efficacious. Small pellets containing cocaine or novocaine,
with adrenalin, are put on the market for this purpose. One of these
pellets is placed in the nail groove, and a drop of alcohol is made to
fall on it. The contents of the pellet are promptly dissolved by the
alcohol, whereupon the operator places his thumb over the nail groove
between the nail and the nail flap and exerts downward pressure. This
forces the dissolved fluid into the tissues, where it acts the same
as if it were injected. This procedure is painful for just a moment
while the pressure is being applied, but the pain soon ceases and nerve
sensibility is lost.
The most generally used method of applying local anesthetics is by
means of the hypodermic syringe and is called the [3]hypodermatic
method. This is preferable to all other forms of inducing local
insensibility, and if the technic is mastered, operations will be
painless with the exception of the initial prick of the needle.
=The Hypodermic Syringe= should be so constructed that it may be
sterilized by boiling. There are many types of such instruments sold,
and in making a selection, only those which will permit such boiling
should be considered. The all-glass syringe or the glass and metal
syringe with the metal piston are best, because the fluid contained
therein is visible, thus preventing the injection of air. Needles
should be of the rust-proof variety and for use in podiatry, they
should be one-half or one inch long and have a twenty or twenty-two
gauge lumen.
After the syringe has been sterilized, it should be adjusted and the
fluid drawn into it after the needle is attached to the barrel. The
entire instrument is then turned, needle up, and the air that may be in
the barrel is expelled by pressure on the piston. When this is done,
the syringe is ready for use.
If the needle is sterile, the only preparation necessary for the skin
is to paint it with tincture of iodine, and then the injection of the
anesthetic may be commenced. The area to be anesthetized is determined,
and then at the most proximal portion, the skin is grasped between the
thumb and forefinger of the left hand. The syringe should be held in
the right hand with the barrel between the first and middle fingers,
and the thumb on the piston. When the skin has been blanched by the
pressure of the fingers of the left hand, the point of the needle,
lumen downward, is thrust into the skin with a quick movement and
immediately after, pressure is brought to bear upon the piston. As the
fluid enters the tissues, it produces a blanched area which is called
a wheal. As the wheal is formed, the needle is gradually moved forward
in the derma until it is inserted as far as the base. It is then
withdrawn, and a second injection is commenced, a little back of the
distal end of the wheal. This second injection, being started in a part
already anesthetized, will cause no pain. So the needle is gradually
moved forward in the derma until the desired area has been covered.
When the deeper tissues are to be anesthetized, the needle may be
directed at an angle to the surface, pressure being borne on the piston
of the syringe as the needle gradually moves deeper into the flesh. It
must be remembered that if the needle is re-inserted into an area that
is already deadened, there will be no pain. The fluid should be ejected
from the syringe slowly, which insures an even distribution of the
drug, as well as comfort to the patient, while the anesthetic is being
administered. Most drugs cause a burning sensation if injected too
rapidly.
The most common lesion for which local anesthetics are used in podiatry
is the ingrown toe nail, and to get good results in these cases,
the technic must be followed in detail. After the derma has been
anesthetized over the region of the nail root and groove, one deep
injection should be made at the root, and vertically to the skin. This
will insure loss of sensation when the root is cut and when the matrix
at this point is curetted.
To prevent the absorption of toxic drugs into the system, some means
should be devised to cut off the circulation during the operation. This
is accomplished by the tourniquet, which is usually made of flexible,
solid rubber, about one-sixteenth or one-eighth inch in diameter and
about a foot long. When this band is tied around the base of the toe,
and pulled tight, it cuts off the circulation. Tourniquets cannot be
used when operating upon the foot proper, and in these cases it is
necessary to be guarded in the use of toxic drugs.
After the use of cocaine[4] or novocaine there is a reaction, and
occasionally the pains produced by this reaction are severe. These
pains may be alleviated to some extent by the use of wet dressings,
but they last only for a short time so that it is often unnecessary
to treat them. The patient should be warned of the reaction. The
local anemia produced by the injection of these drugs is subsequently
followed by hyperemia, and it is therefore necessary to guard against
hemorrhage in cases in which free incisions have been made. Wounds
should be packed, and proper bandages should be applied to prevent any
such possibilities.